In the case of a bottom-gate TFT as a type of organic thin film transistor (organic TFT), two types of electrode structures are known, such as a top-contact structure with source/drain electrodes formed on a channel forming region including an organic semiconductor layer and a bottom-contact structure with source/drain electrodes formed below a channel forming region (see, for example, Advanded Materials vol. 14, p. 99 (2002), C. D. Dim itrakopoulos, et al.). Furthermore, also in the case of a top-gate TFT, two types of electrode structures are known, such as a top-contact structure with source/drain electrodes formed on a channel forming region and a bottom-contact structure with source/drain electrodes formed below a channel forming region.
In the case of the bottom-contact structure, high-definition electrode patterning is possible which uses a lithography technique. Therefore, in the case of achieving high integration, the bottom-contact structure is often adopted. Further, in order to improve the charge injection efficiency from the source/drain electrodes into the organic semiconductor layer, an attempt has been made to modify the surfaces of the source/drain electrodes with a thiol compound or a silane coupling agent. However, the bottom-contact structure has, due to differences in mechanical characteristic value between the source/drain electrodes and the channel forming region, problems such as difficulty in controlling strain caused at the interface on flexion or on heating, thereby leading to decreased reliability of the TFT.